According to the Library of Congress website:
The Library of Congress was created on April 24, 1800 by President John Adams when he approved legislation that appropriated $5,000 to purchase "such books as may be necessary for the use of Congress." The original collection consisted of 740 volumes and three maps.
When the Library of Congress building opened its doors to the public on November 1, 1897, it was hailed as a glorious national monument and "the largest, the costliest, and the safest" library building in the world.
Today, a complex of three buildings in Washington, D.C. comprise the Library of Congress. Over 147 million items in over 450 languages are housed there, making the Library of Congress the largest library in the world.
The Library receives some 22,000 items each working day and adds approximately 10,000 items to the collections daily. The majority of the collections are received through the Copyright registration process.
If you're in Washington, visit this world-famous library!